Tribological properties of ion implanted UHMWPE against Si3N4 under different lubrication conditions

Wear is the primary cause of failure of joint replacement prostheses. In this paper, the ultrahigh molecular weight polyethylene (UHMWPE) was implanted with O+ and C+ ions at different energies and doses. Its friction and wear behaviors were studied under dry friction, lubrication of distilled water and blood plasma using a pin-on-disk tribometer with a Si3N4 ceramic ball as the counterface. Scanning electron microscopy was used to examine the surfaces of un-implanted and implanted UHMWPE before and after wear. The experimental results show that the wear resistance of the implanted UHMWPE is higher than that of the unimplanted UHMWPE under dry friction, lubrication of distilled water and blood plasma. The wear resistance of the O+-implanted UHMWPE is better than that of the C+-implanted, especially for 450 keV energy and 5 X 10(15)/cm(2) dose O+-implanted sample, of which the wear rate is the lowest. The wear rates of the implanted and un-implanted UHMWPE are higher under dry friction than under the blood plasma lubrication. The adhesion, ploughing and plastic deformation are the wearing mechanisms for the un-implanted UHMWPE, while the fatigue and abrasive wear for the implanted UHMWPE. (C) 2003 Elsevier B.V. All rights reserved.